"The army said in a statement that it had taken the action to 'keep peace and order,' and soldiers entered several private television stations that are sympathetic to protesters.

"A ticker on Channel 5, an army station, however, denied the military was taking over, saying 'the invocation of martial law is not a coup.' "

"The public do not need to panic but can still live their lives as normal," the announcement said, according to a translation used by the BBC.

Michael Sullivan, reporting for NPR from the northern Thai city of Chiang Rai, says "the early morning announcement ... came as a surprise to many and it's unclear whether it will exacerbate the country's political crisis or help end it."

After months of protests, Yingluck and nine of her Cabinet ministers were ousted by Thailand's Constitutional Court after she was found to have abused her powers when she transferred the national security chief, who was appointed by the opposition.

But the opposition that sought her removal has continued its push to have what's left of her government removed. Opposition leaders have called for an unelected council to rule the country.

Coups are nothing new to Thailand. The last one took place in 2006 and removed Yingluck's brother, Prime Minister Thaksin Shinawatra, from office. Since the end of the absolute monarchy in the country in 1932, the military has staged 11 successful coups.

The opposition had openly invited the military to stage another coup to remove Yingluck, a request that was rebuffed until December, when the army chief in an interview declined to rule out the possibility.

Asked whether the army would seize the government for the second time in less than a decade, Gen. Prayuth Chan-ocha said: "That door is neither open nor closed. ... It will be determined by the situation."

The months of political uncertainty and street protests in Thailand have also taken a toll on the second-biggest economy in Asia, contributing to falling private consumption and investment and negative GDP growth, Reuters reports.

The news agency says:

"The political turmoil is also hurting Thailand's big auto sector, which accounts for 11% of GDP and is the largest in Southeast Asia. Domestic car sales are falling and some 30,000 industry jobs have been lost his year.

"Thai Airways last week reported a quarterly loss and expects more red ink in the second and third quarters as 'we have been severely affected by the politics,' chairman Prajin Juntong said.

"Tourism accounts for about 10% of GDP and visitors dropped about 5% in January-April from a year earlier."